X @Avi Chawla

Mixture of Experts (MoE) Architecture - MoE is a popular architecture leveraging different experts to enhance Transformer models [1] - MoE differs from Transformer in the decoder block, utilizing experts (smaller feed-forward networks) instead of a single feed-forward network [2][3] - During inference, only a subset of experts are selected in MoE, leading to faster inference [4] - A router, a multi-class classifier, selects the top K experts by producing softmax scores [5] - The router is trained with the network to learn the best expert selection [5] Training Challenges and Solutions - Challenge 1: Some experts may become under-trained due to the overselection of a few experts [5] - Solution 1: Add noise to the router's feed-forward output and set all but the top K logits to negative infinity to allow other experts to train [5][6] - Challenge 2: Some experts may be exposed to more tokens than others, leading to under-trained experts [6] - Solution 2: Limit the number of tokens an expert can process; if the limit is reached, the token is passed to the next best expert [6] MoE Characteristics and Examples - Text passes through different experts across layers, and chosen experts differ between tokens [7] - MoEs have more parameters to load, but only a fraction are activated during inference, resulting in faster inference [9] - Mixtral 8x7B and Llama 4 are examples of popular MoE-based LLMs [9]